{
	let protocol = 'http';
	let appHost = protocol + '://' + window.location.host;
	let reqURL = appHost + '/footer.html';

	let xhr = new XMLHttpRequest();
//监听状态的改变
	xhr.onreadystatechange = function () {
		if (xhr.readyState === 4 && xhr.status === 200) {
			document.write(xhr.responseText);
		}
	};
//1.请求方式  2.发送到哪去  3.是否为异步请求 是true 否 false
	xhr.open('get', reqURL, false);
//开始请求，Post可发送数据
	xhr.send();
}